Principal Token (PT): Represents the underlying asset, and upon maturity, PT can be redeemed for the underlying asset on a one-to-one basis. For instance, 1 PT-stETH can be redeemed for 1 ETH worth of stETH.
Yield Token (YT): Allows investors to receive the yields generated by the underlying asset. For example, holding 10 YT-stETH enables investors to receive all yields generated by 10 ETH deposited into Lido.